The State Department hailed the International Civil Aviation Organization (ICAO) today for adopting an American proposal to combat air piracy. Department spokesman Charles Bray said it “marks a significant step forward.” The ICAO meeting yesterday in Montreal voted 17-1 in favor of an American proposal to convene a global diplomatic conference next Aug. on means to discourage aerial hijackers.

It also instructed its legal committee to meet next Jan. to prepare the ground work for an international convention on skyjacking for consideration by the conference. Egypt cast the sole negative vote. Eight members abstained, including the Soviet Union and France.

The convention is expected to incorporate a US proposal calling for the suspension of air services and possibly a secondary boycott of air services to any country that does not abide by the three previous international conventions providing for the extradition or prosecution of hijackers and saboteurs of air traffic.

President Nixon yesterday signed the Montreal Sabotage Convention of 1971, ratified by the Senate Oct. 3. Signatories must prosecute or extradite saboteurs and hijackers seeking refuge in their countries. Nixon said his special Cabinet committee on terrorism has “taken steps to insure that stricter controls are placed on visa applications and visa extensions of possible terrorists.”